For the code to work you have to be in a
destination driving mission. 
After pausing the game pick City map and press Left, Right,
Left, Right, X
Heavier Car
For the code to work you have to be in a
destination driving mission. 
After pausing the game pick City map and press Down, Down, Down,
X.  For this to work you have to be in a car before opening the
city map.